| Sandwich plate structures have been used widely in many fields like mechanical due to their light weight,high strength and vibration/noise reduction.Their performance is dependent on the stiffener layout pattern to a great deal. The commonly used topology optimization method can only get a vague stiffener distribution area and the existing bionic optimization design researches can only solve limited engineering problems. Inspired by the morphogenesis mechanism of dicotyledonous venation, this paper is to develop a universally applicable and straightforward approach to provide the explicit layout design of stiffened plate/shell structures without complicated postprocessing. The current mechanical property study of the bionic stiffened plate structures usually focus on statics characteristic and fundamental frequency analysis, frequency response under dynamic load is supplied in this paper. Besides,the sound insulation performances of the bionic stiffened sandwich plate such irregular complex structure is considered for further analysis of vibration and noise reduction. To prove that biomimetic method not only provide inspiration for mechanics, also provides new ideas for the acoustics. The major work of this thesis is showed as followed:The venation-inspired growth optimization method for stiffener layout design of sandwich plate structures was introduced. The growth model and algorithm flow was established that the stiffeners extend by obeying a similar growth rule as the venation. The growth and degeneration of the stiffeners are determined by elemental sensitivity numbers. the recommended key parameters were determined, including seeds position, the degeneration rate and convergence degree. The numerical model of sound-vibration coupling for stiffened sandwich plate was established, the effect produced by stiffeners for vibro-acoustic of sandwich plate structures was introduced.The mechanics properties of the bionic stiffened sandwich plates obtained by this method were studied though three typical examples(unilateral clamped plate with concentrated load on edge, four corners clamped plate and adjacent edges clamped plate with concentrated load on center). Compared with the orthogonal stiffened sandwich plates and no-stiffened sandwich plates, the bionic stiffened sandwich plates show excellent statics and dynamics performance.Results show that the low order natural frequencies of bionic stiffened sandwich plates higher than that of orthogonal stiffened sandwich plates increased to varying degrees; the fundamental frequency increased 7%-9.6%; maximum deformation under dynamic load reduced 27.8%-36.4%.The sound insulation performances of the bionic stiffened sandwich plates obtained by this method are studied also though three typical examples. The sound insulation frequency characteristic curve of typical honeycomb sandwich plate was analyzed and calculation model of the sound insulation was established by using the coupled boundary element and finite element method. Sound insulation of the same stiffened sandwich plates filled with different liquid was analyzed, sound insulation of different honeycomb-core sandwich plate was analyzed, the sound absorption coefficient of three kinds of sandwich plate structure was contrastively analyzed. Compared with the orthogonal stiffened sandwich plates and no-stiffened plates, the bionic stiffened sandwich plates show excellent sound insulation performances. The transmission loss of bionic stiffened sandwich plates under stiffness control area improved 1.5-4.2dB than that of orthogonal stiffened sandwich plates; resonant frequencies moves to the higher frequency and minimum values increase; in different frequency band, different honeycomb-core has less influence on the sound insulation;comparison between no-medium orthogonal stiffened sandwich plates and filled with different kinds of liquid, results show that the dense is higher, the effect of sound insulation is better, the transmission loss of sandwich plates filled with dichloromethane improved 1.4dB than that filled with water, improved 4.9dB than that filled with nothing.Using unilateral clamped plates as example,comparative experiments of stiffened panels with different configuration was conducted. Natural frequencies were measured by hammering method; Reverberation ventricular-sound elimination box was designed to measure sound transmission loss. Comparison analysis between numerical examples and experiment results indicates that numerical calculation is efficient. Besides, the proposed venation-inspired bionic optimization method can be applied to the stiffener design to improve the structural static,dynamic mechanical properties and sound insulation property. |
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